Apt Holman Preamplifier Review (vintage Audio)

[EJ3]

True. My son didn't buy a 67 Camaro shell to save money. A new one would be cheaper and he could drive it now. It was for the love of the game.

But if you already have a great, well kept, 67 Camaro with all the amenities you need (AC/PB/4 wheel disc brakes, electronic fuel injection [or perhaps an LT4 engine] that you have upgraded over the years, then I personally wouldn't get a new one. I'd just keep driving & upgrading what I have. & enjoy the music. At some point I'll add digital to the mix. A large part of it is "Because I can". And want to.
But, because I already have it, in a way, it does save money. Because I have gotten to enjoy it all these years.
When I have bought a new or close to new car & paid it off in a couple/three years, then I keep making the payment to my bank. I would not have bought the car if I didn't like it but in a year I'll want to add or change something. Well, the money is there to do that because I just kept paying it, only to my "do what I feel like doing" fund. Same with the stereo. One day, maybe no more upgrades will be helpful to what I have. Then it will be time for a different (possibly but not necessarily new) model.

 

[YSC]

Really nice one! at first the channel imbalance hurts my eyes (yea it's likely not perceivable, but you know... graphs hurts eyes)

Then I noticed there's a balance knob

 

[EJ3]

Really nice one! at first the channel imbalance hurts my eyes (yea it's likely not perceivable, but you know... graphs hurts eyes)

Then I noticed there's a balance knob

Looks like the 1st of two graphs that show a channel is .25 Db. The second one is "God forbid!" a whole Db! There is actually an internal adjustment to fix that.

For further information see:

Apt Holman Preamplifier Service Manual.

Audio magazine, October 1978, pages 36 and 187 (ads).

Audio magazine, October 1979, page 42 (ad).

Audio magazine, February 1980 (review).

Audio magazine, October 1982, page 14, left side (ad).

Audio magazine, October 1983, page 217 (talks about Preamplifier 2 and the stereophony circuits).

 

[Alice of Old Vincennes]

But if you already have a great, well kept, 67 Camaro with all the amenities you need (AC/PB/4 wheel disc brakes, electronic fuel injection [or perhaps an LT4 engine] that you have upgraded over the years, then I personally wouldn't get a new one. I'd just keep driving & upgrading what I have. & enjoy the music. At some point I'll add digital to the mix. A large part of it is "Because I can". And want to.
But, because I already have it, in a way, it does save money. Because I have gotten to enjoy it all these years.
When I have bought a new or close to new car & paid it off in a couple/three years, then I keep making the payment to my bank. I would not have bought the car if I didn't like it but in a year I'll want to add or change something. Well, the money is there to do that because I just kept paying it, only to my "do what I feel like doing" fund. Same with the stereo. One day, maybe no more upgrades will be helpful to what I have. Then it will be time for a different (possibly but not necessarily new) model.

Not sure I follow you.

 

[EJ3]

Hmmz. It has a dedicated headphone amp.
View attachment 167076
The switches that are kind of poorly labelled operate like this.>
View attachment 167077
View attachment 167078

Stereo Mode Controls

Leave the MODE knob in the middle at STEREO, and leave the L > R and R > L switches down for normal stereo.

For mono, turn the knob to the left. The left-side of the control slowly narrows the image from stereo into mono. Controls like this were popular in the 1960s because people, used to mono, were sometimes uncomfortable with the full stereo effect.

Turning the knob to the right expands the stereo image. It mostly just sucks out the center of the image.

The L > R and R > L switches select what input channels go to what output channels.

Here's what they do:

L > R	R > L
down	down	Normal Stereo
UP	down	Left channel input heard as mono in both output channels
down	UP	Right channel input heard as mono in both output channels
UP	UP	Reversed Stereo

If you'd like more detail, Tom ran out of panel space to label these more clearly as MONITOR INPUT SELECT RIGHT and MONITOR INPUT SELECT LEFT, which is what they're really doing.

If you lift the L > R switch, it puts the left channel into the right channel. The left channel remains in the left channel. You now are listening to the left channel (in mono of course) in both channels.

Lifting the R > L switch does the same thing, playing the right channel in both channels.

Lifting both switches at the same time simply flips the channels: left goes to right, and right goes to left.

These two switches allow the six line-level stereo inputs (including the tape and EPL loops) as up to twelve discrete mono inputs! This feature was popular in the 1960s, when mono tuners, phonographs and tape decks had but one output connector.

 

[EJ3]

Not sure I follow you.

If you already have the equipment, then you are only upgrading or modding it. There is no purchasing it anymore, as you did that years ago. Amortizing what you add to the price by maintenance & upgrading is not the same as purchasing vintage equipment that needs a major investment in refurbishment.

 

[EJ3]

Infrasonic Filter

The infrasonic filter switch is on the rear panel, near the phono inputs.

Press it IN to remove record warp and turntable rumble. In some digital classical recordings, it will remove low-level infrasonic noise from passing trucks and air conditioning originally present in the recording venue.

The purpose of this filter is to remove subsonic noise that itself is inaudible, but which often can cause speakers or other components to distort. If you see your woofers floating in and out, this filter will stop this excess motion without affecting the music, and stops any Doppler or intermodulation distortion that this cone flutter otherwise could cause.

Leave this filter OUT otherwise. It has no audible affect on good recordings, and reduces infrasonically-induced distortion on records or some classical recordings.

It is an 18 dB/octave high-pass filter -3dB at 15 Hz.

When selected, it is active for every input and every output. The tone controls need not be active, as they must be for the High Filter.

 

[restorer-john]

The service manual is just a joy isn't it?

 

[EJ3]

The service manual is just a joy isn't it?

Considering that it is also the owners manual, yes!
For the uninitiated, the "Stereo Mode Controls" are not entirely self-explanatory to some so an explanation is needed.
Although, I believe most folks would grasp it once they played with it.

Also not entirely comprehensible to some is:
Bass Mode

This switch controls the turnover frequency of the bass control.

Lifted, the "shelving" position, the bass control has somewhat less effect than more common bass controls. It affects the lower frequencies without altering the lower midrange as much as ordinary bass controls.

The lower setting controls only the deepest bass. Its effect is even more subtle than the upper position.

Lifted is subtle & lower is even more subtle. Not at all like 'normal' BASS tone controls.



High Filter

Use this filter to remove noise from scratchy records or AM radio.

This is a 12 dB/octave low-pass filter at 8 kHz. It is only active with the tone controls active.

I never use this filter. It's too sharp and at too low a frequency for use with better recordings.

Any time the tone controls are active and this filter isn't selected, a 40 kHz filter is selected instead.

And there are these few rather entertaining things (I especially like why you would want to use the 'MUTE' feature)

MAIN 2 Output

There are places on the circuit board for our technician to replace jumpers with a resistive pad for the MAIN 2 output, if needed to optimize the gain structure for your power amplifier.

Mute Switch

Be sure to hit this when you put in your headphones. The output to your power amplifiers does not mute automatically.

Laboratory Trick

If using the Holman Preamplifier in a laboratory, it might be handy to have a licensed technician readjust the the volume control knob so that unity gain is straight-up.

Quadraphonic Synthesis

With two Holman Preamplifiers, you can synthesis and control four output channels from just two input channels.

Apply all your inputs to the first Holman Preamplifier. Use it for all your tone controls, filters and source and tape selections. Leave its Stereo Mode in Stereo.

Connect the first Holman Preamplifier's MAIN 1 output to one power amplifier and your two front speakers.

Connect the first Holman Preamplifier's MAIN 2 output to any line-level input of the second Holman Preamplifier.

Connect the second Holman Preamplifier's MAIN 1 output to the power amplifier for your two rear speakers.

Rotate the second Holman Preamplifier's stereo mode control to L-R, and start by setting it to about unity gain or a bit less, and keep its tone controls flat. The tone and filter settings of the first Holman Preamplifier are fed automatically to the second Holman Preamplifier.

Set balance on the first preamp. Set front-rear balance on the Volume control of the second preamp.

Leave the power switch of the second preamp ON, and plug its power cord into a switched outlet of the first Holman Preamplifier. Now the power is controlled by the first Holman Preamplifier, too.

 

[Doodski]

The service manual is just a joy isn't it?

Yes, I skimmed and scanned it and it's nice. Telephone number on the front page. I like where they recommend a Tektronix O-scope or a HP, a Simpson 260 multimeter, HP 3580A (they are still in use today.), a list of the hand tools required. The only thing missing in the recommended test gear is a Sencore Cricket transistor/FET tester. I loved that device, I had a very well used one handed down to me by a old techy that said this is what is needed and it saved my donkey many times. If you don't have one I recommend getting one for your lab.

 

[Labjr]

It's neat but I wouldn't buy something like this now. Even line a level signal goes through too many components. You could probably build something that would outperform this with a couple op-amps.

 

[Doodski]

It's neat but I wouldn't buy something like this now. Even line a level signal goes through too many components. You could probably build something that would outperform this with a couple op-amps.

But would it have all the features and capability of the Apt. Plus the romance and history.

 

[Labjr]

But would it have all the features and capability of the Apt. Plus the romance and history.

Most of those features aren't needed anymore. Would only need a buffer. Possibly a little gain. Volume control and a source selector.

 

[Doodski]

Most of those features aren't needed anymore. Would only need a buffer. Possibly a little gain. Volume control and a source selector.

No bass and treble, balance or loudness control?

 

[restorer-john]

No bass and treble, balance or loudness control?

Real preamplifiers are built with features like the Holman.

Proper preamplifiers need phono stages, bass, treble, balance, filters, defeats, multiple tape loops, plenty of inputs, MC stages, several outputs and of course switched and unswitched outlets.

These silly little stripped down single gain stages in a box sold these days as 'preamps' are an insult to hi-fi. But then again, today's 'audiophiles' rarely stray outside a USB connection, a single XLR input and maybe a legacy line RCA.

We can't bring back the good old days, but we sure can enjoy the gear that was built to be operated, built to last and still performs well 40+ years on.

 

[Blumlein 88]

Real preamplifiers are built with features like the Holman.

Proper preamplifiers need phono stages, bass, treble, balance, filters, defeats, multiple tape loops, plenty of inputs, MC stages, several outputs and of course switched and unswitched outlets.

These silly little stripped down single gain stages in a box sold these days as 'preamps' are an insult to hi-fi. But then again, today's 'audiophiles' rarely stray outside a USB connection, a single XLR input and maybe a legacy line RCA.

We can't bring back the good old days, but we sure can enjoy the gear that was built to be operated, built to last and still performs well 40+ years on.

I don't do vinyl anymore. So I've ended up using a recording interface with lots of ins and outs for what much of a preamp once did. You can then also use the output for a DAC or send the digital result to a separate DAC. Some of these interfaces now can be controlled by phone or iPad making them even easier to put at the center of your system for controlling everything going to your amps.

 

[Doodski]

Some of these interfaces now can be controlled by phone or iPad making them even easier to put at the center of your system for controlling everything going to your amps

I decentralized everything. No more cel tel controlling stuff. Yeah, Ima a weirdO!

 

[Blumlein 88]

I decentralized everything. No more cel tel controlling stuff. Yeah, Ima a weirdO!

I don't know if mine is decentralized. My problem the last 18 months is a floating configuration. I've multiple possibilities with different advantages. I can swap over in a couple minutes or less to each. This is mostly on the digital source end, the playback end is stable. I think it will evolve into a home network distributed system that my good Stereo can access in various ways.

 

[restorer-john]

I decentralized everything. No more cel tel controlling stuff. Yeah, Ima a weirdO!

Same here. I don't see myself giving up on my physical media until I am really old, and maybe even then, I won't.

There's way too much joy to be had, getting out an absolutely mint CD, one perhaps I've had for nearly 40 years and listening to it. Playing the same ripped track via a device attached to my network and controlled by a stupid phone or tablet just has zero satisfaction for me.

Walking across the room to operate a volume control or change a track is also what I like. Most of my newer vintage gear is of course remote, but the remotes languish in the drawers (batteries removed). The only thing I want in my hand while listening to music is a glass of red wine and maybe the next disc in my impromptu evolving playlist du jour.

 

[Doodski]

I don't know if mine is decentralized. My problem the last 18 months is a floating configuration. I've multiple possibilities with different advantages. I can swap over in a couple minutes or less to each. This is mostly on the digital source end, the playback end is stable. I think it will evolve into a home network distributed system that my good Stereo can access in various ways.

Can it be done without a cel tel and still be and have the control distributed around the abode? Access from rooms integrated into the system or does that require new construction, new design and hardware installation? Can it be full wireless and not require a cel tel accessing via internet service?